1. What is the meaning of Null data type?

Null is nothing, the data type of null is an object. A variable with an unknown value can store Null.

NaN means for ‘Not a Number ’. Like,

2. Falsy value: JavaScript has some values ​​that the JavaScript compiler assumes to be false values.😒- false, 0, null, undefined, Nan, Empty String(“ ”).

3. What is the difference between == and === operators?

‘=’ operator is used for assigning values to a variable.

‘==’ operator is used for comparing two variables, but it ignores the datatype of the variable.

‘===’ operator is used for comparing to variables and also checks datatype and compares two values.

4.Object literal in js: A JavaScript object literal is a comma-separated list of property/ attribute and method in curly braces.

we can use a method into an object and we can call it like rect.draw(). But what if you use the property inside that function? What is this?🤦‍♂️🤦‍♂️

5.how to understand the this keyword?

point 1- this will always refer to the object that will be used. point 2-
If the object uses this somewhere else, it will always refer to the window object.

But if we use this inside an object, will the object refer? Yes, Then who will refer to the object that will be used. Follow the example of point 4.

6.Bind, call, Apply: When a function is called, the this keyword always refers to the window object. But what if we want to use the object we created?
There are 3 methods for this. Call, Bind, Apply….

7.What is Synchronous programming?

Synchronous means that you can only execute one thing at a time. (existing and occurring at the same time)-line by line execution.

8.What is Asynchronous Programming?

Asynchronous means that you can only execute multiple things at a time and you don’t have to finish executing the current thing in order to move on to the next one. (not existing and occurring at the same time)

9.What Does V8 engine do?

• Compile and Executes js code
• Handling call stack
• Handling Heap Memory for variables
• Provide Data types, Operators, Objects, and Functions.

10. What is DOM?

It just an API to interact with HTML Document and change it later on-demand. With the HTML DOM, js can access and change all the elements of on HTML document. when a web page is loaded, the browser creates a DOM of the pages. The HTML DOM model is constructed as a tree of objects.

Javascript 10 Question ✌✌ was originally published in JavaScript Power Play on Medium, where people are continuing the conversation by highlighting and responding to this story.

***The special advantage of the function is that it reduces code duplication.

Function Declarations :

Function invoking: Declaring a function does not execute immediately. The function for this is to call. And this call is called function invoking. In other words, using the function is function invoking.

IIFE: A js immediately invoked function expression(IIFE) is used if you need to call immediately after creating a function.

The Arguments Object: We do not know how many arguments the user will pass when calling the function, again the number of parameters to be given in the function is not fixed. To solve this problem there are argument objects. JS functions have a built-in object called the arguments of object. Change the arguments are not visible outside the function.

This means that I can access the arguments sent from outside by the argument keyword inside the function.

Function Expression: Expression means that evaluates to a single value from the valid set of literals, variables, operators. Like,5+ 5 =10. It is a simple expression that evaluates a single value of 10. But what is the Function Expression??

A function expression can be stored in a variable. Then you can call that variable and work.

Actually, this function is called the Anonymous function because it has no name. Here add is a variable but acts like a function. We know that Expressions always in a single value. And above function return a single value.

Scoping: Scope controls where a variable is declared and where it can be accessed. In js two types of scope:

1. Local Scope- Each function creates a local scope. The variable declared in the local scope cannot be used outside that scope
2. Global Scope- A Global variable has global Scope. Variables declared in Global Scope can be used in any scope. It can be used in a functional scope. But the variable declared in the local scope cannot be used outside that scope.

JS Hoisting: When to declare a variable, when to assign a value, when to reassign a value, when to use that variable. All of this is the job of hosting. Like, a variable can't be used after declared.

Functional Programming: The role of functional programming is to avoid shared state, mutable and side effects. When a function behaves like a value, it is called Functional Programming.

there are three main terms……..

1. Pure functions 2. First-class functions 3. Higher-order function

What is Pure Function?

• ** It returns the same result if given the same arguments
• **It does not cause any observable side effects

the above function is not a pure function because it modified a state point.x and point.y outside its scope.

it is a pure function. It didn't side effect the external state.

What is a First-class function?

• ** A function can be stored in a variable.
• ** A function can be stored in an array
• ** A function can be stored in an object
• ** We can create function as need

High Order function :

• ** We can pass a function as an argument.
• ** We can return function from another function.

Closure: If data comes from an outside scope inside a scope, then that scope is called its closure. (bahirer duniay thaka kono kichu ke carry kore/ variables that are used locally but defined in an enclosing scope)

JavaScript Function, Expression, Scope, Hoisting, Closure. was originally published in JavaScript Power Play on Medium, where people are continuing the conversation by highlighting and responding to this story.

The number type is the primitive data type. It is defined by JavaScript. A number is a primitive object used to represent and manipulate numbers like 20 or -17.

NaN property- The NaN property means Not a Number. This property indicates which value is not a pure number.

isNaN() -Use the isNaN() function to check which value is NaN or Not .If the value is NaN it returns true otherwise false.

Number()- The Number() function used to convert any value to a number but if the value can not be converted to a pure number, its return NaN.

parseFloat()- This function parses a string and returns a floating number.
If the value can not be converted to a floating point, its return NaN. Some examples are given below.

parseInt()-This function parses a string and returns an integer.
If the value can not be converted to an integer, its return NaN. Some examples are given below.

Math- Math is a built-in javascript Object. It has some properties and methods for mathematical operation. Some properties and methods are given below.

Math.abs()- This function returns the absolute value of a number.Like, it returns a number of n if n is positive or zero or negative otherwise it returns NaN. Only it returns 0 if you pass empty string/array/null.

Math.ceil()- Converting a decimal number to a whole integer number always returns the largest around value.

Math.floor()-Converting a decimal number to a whole integer number always returns the smallest around value.

Math.min()- This function returns the lowest value from a set of numbers.

Math.max()- This function returns the highest value from a set of numbers.

Math.random()- The random method returns a random number between 0(inclusive) and 1 (exclusive).

Math.round()-Converting a decimal number to a whole integer number always returns a rounded value.

Math.sqrt()- The Math.sqrt() function returns the square root of a number.

Math.pow()- This function has two-parameter . It calculates the value by the way of x^y.

Thanks everyone for continuing. Please follow my publication.

The most common uses of JavaScript Number and Math Methods was originally published in JavaScript Power Play on Medium, where people are continuing the conversation by highlighting and responding to this story.

A string is any text inside a single quote or a double quote. Like “Hossen Mohammad”/ ‘Hossen Mohammad’

Let’s get to know the ninja tricks of the most used method of JavaScript.

1. charAt()-This method returns the specific index or position of each character in the string. This means that you can find out the position of any character in the string with this method. Let’s look at an example…

2.concat()-The function of this method is to add one or more strings and return a new string. like ….

3.includes()- The includes() method determines whether a string contains the characters of a specified string. If the characters are in the string, True returns otherwise false…..

4.endsWith()- the includes() method determines whether a string ends with the characters of a specified string. If the characters are at the end of the string, True returns otherwise false….

5.indexOf()- The indexOf() method returns the position of the first occurrence of a specified value in a string.
Note: If it does not match, then -1 return

6.lastIndexOf()- The indexOf() method returns the position of the last occurrence of a specified value in a string.
Note: If it does not match, then -1 return.Same as indexOf() but indexOf() returns first occurrence.

7.replace()- This method finds the string of a particular character and replaces it. In this case, it replaces the one with the match at the beginning.

8.slice()-The slice() Method pulls out a segment from a string. And the extracted part returns as a new string.

9.split()-The split method splits a string into a substring and returns it through an array.

10.startsWith()-The startsWith() method returns true or false values ​​based on what character string of a string it started with.

Note: startsWith() is case sensitive

11.substr()-This method is used to create another string by taking parts from one string. The first value of this method is the starting value. That is the index number from which the extraction will start. And the last value is how many characters the string will contain.

12.toLowerCase()-The toLowerCase() method converts each letter of the string to a letter in Lowercase.

13.toUpperCase()-The toUpperCase() method converts each letter of the string to a letter in Uppercase.

14.trim()-Removes white space on both sides of the string.

15.trimEnd()-Removes the white space on the right side of the string

16.trimStart()- Removes the white space on the left side of the string

The most widely used JavaScript string method was originally published in JavaScript Power Play on Medium, where people are continuing the conversation by highlighting and responding to this story.